Latest Facebook Messenger 203 user agents:

User Agent Platform Device
Mozilla/5.0 (Linux; Android 8.1.0; Redmi Note 5 Build/OPM1.171019.011; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/72.0.3626.105 Mobile Safari/537.36 [FB_IAB/Orca-Android;FBAV/203.0.0.21.91;] Android 8 Redmi Note 5
Mozilla/5.0 (Linux; Android 5.1.1; SM-J320FN Build/LMY47V; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/55.0.2883.91 Mobile Safari/537.36 [FB_IAB/Orca-Android;FBAV/203.0.0.21.91;] Android 5 Galaxy J3 (2016)
Mozilla/5.0 (Linux; Android 5.1.1; SM-J120F Build/LMY47X; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/56.0.2924.87 Mobile Safari/537.36 [FB_IAB/Orca-Android;FBAV/203.0.0.21.91;] Android 5 Galaxy J1 (2016)